Theory and measurement of the angle of arrival and time delay of UHF radiowaves using a ring array

The knowledge of directions of arrival (DOA) of waves is fundamental in understanding the physics of the mobile communications wide-band propagation channel. We first present a measurement setup that is able to accurately measure these DOA. It is based on the evaluation of the channel complex impulse response at regularly spaced locations on a circle. We theoretically investigate a new approach for deriving the DOA from this ring array. We then describe an experimental campaign, where such measurements were done on a building rooftop. We show that all the main paths are clearly retrieved and identified and that the ray theory is valid and applicable. The results emphasise the predominant role of UHF-wave specular reflection by walls in an actual urban environment.